System for opening and closing a flap

ABSTRACT

A system for opening and closing a motor vehicle, the flap is swivalably mounted along one of its edge areas at a stationary structural component part about a horizontal swiveling axis. A first drive device and a second drive device act in parallel to more like flap from a closed position into an open position. The first drive device is a non-self-locking drive device, and the second drive device comprises a cylinder filled with a fluid under pressure. An interior of the second drive device is divided by a piston into a first work chamber and a second work chamber, wherein a piston rod of the piston is guided outward through the first work chamber. A valve arrangement in the piston closes a flow connection between the first work chamber and the second work chamber in a stationary operating state of the flap.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a system for opening and closing a flap for amotor vehicle mounted along one of its edge areas to a stationarystructural component so as to be swivelable around a horizontalswiveling axis. The flap is driven by a first drive device and a seconddrive device acting in concert so as to be movable from a closedposition into an open position, wherein the first drive device is anelectromechanical drive device and the second drive device is ahydraulic, pneumatic, or hydropneumatic drive device.

2. Description of the Related Art

Opening and closing systems for vehicle flaps are known for opening andclosing flaps such as hatchbacks, trunk lids, engine hoods, doors, andthe like in motor vehicles. Often, both sides of the flap are drivenelectromechanically so as to prevent warping of the flaps when the flapsare open and closed.

Some drive systems are used that drive the flaps electromechanically ononly one side, while a gas spring is arranged at the other side of theflap. The gas spring counterbalances the weight of the flap bysubstantially supporting only the opening of the flap. An opening andclosing system of this kind is generally better than the variant that isdriven electromechanically on both sides and is therefore preferred forinstallation in most applications.

In systems that are driven electromechanically on one side it isdisadvantageous that the electromechanical drives are outfitted withpressure springs, typically embodied as helical pressure springs, whichmust counterbalance the weight of the flap so that the motor hasreasonable dimensions in terms of the vehicle construction and the flapcan be safely held in a partially closed position or in the completelyopen position.

Further, it is disadvantageous with respect to installation space whenthe flap is stopped in desired positions by other braking elements orclamping elements.

SUMMARY OF THE INVENTION

Therefore, it is an object of the invention to provide an opening andclosing system for flaps that overcomes the disadvantages describedabove and has a simple, space-saving construction with few structuralcomponent parts.

According to one embodiment of the invention, the first drive device isa non-self-locking drive device and the second drive device comprises acylinder that is filled with a fluid under pressure and whose closedfirst end is connected to the stationary structural component part orflap at a distance from the swiveling axis. The interior of the seconddevice is divided by a piston into a first work chamber and a secondwork chamber, wherein a one-sided piston rod of the piston is guidedoutward through the first work chamber and out of the first work chamberso as to be sealed by a sealing and guiding package and is connected tothe flap or stationary structural component part at a distance from theswiveling axis, with a valve arrangement by which a flow connectionbetween the first work chamber and the second work chamber is closed ina stationary operating state of the flap.

The flow connection between the first work chamber and the second workchamber is opened during a movement of the flap so that a fluid balanceis achieved between these two work chambers.

When flap movement is concluded, the flow connection is closed and theflap is held in its occupied position.

The first drive device is preferably arranged at a first edge area ofthe flap and the second drive device is preferably arranged at a secondedge area of the flap, which proceeds at least approximately at rightangles from the swiveling axis.

This configuration limits warping of the flap due to an imbalancedapplication of force.

The flap can be a hatchback, a trunk hood, engine hood, or the like inthe motor vehicle.

The flap is preferably supported along its upper edge area so as to beswivelable around the swiveling axis and is directed substantiallyperpendicularly downward in the closed position and substantiallyhorizontally in the open position.

Because a fluid equilibrium is blocked when the flow connection isclosed, the flap remains securely held in its occupied position even inhorizontal orientation.

It is particularly economical in terms of space when the first drivedevice has a spindle drive driven in rotation by a rotary drive andwhich has a threaded spindle that is connected to the flap or to thestationary structural component part, and a spindle nut that is arrangedon the threaded spindle that is connected to the stationary structuralcomponent part or to the flap.

To reduce the rotating speed of the rotary drive, the threaded spindleis driven in rotation by the rotary drive by a non-self-locking gearunit. Due to the non-self-locking construction of the gear unit, as wellas the non-self-locking construction of the entire drive device, theflap is easily moved by hand when the first drive device is notactivated. The rotary drive is preferably an electric motor.

When the rotary drive, threaded spindle, spindle nut and, the gear unitare all preferably arranged in a tubular housing, a compactconstructional unit is achieved which protects these components.

A spindle tube preferably encloses the threaded spindle with play and isconnected to the spindle nut by its axial end that is closer to therotary drive and can be articulated at the stationary structuralcomponent part or the flap by its end remote of the rotary drive.

In a preferred embodiment, the protective tube is arranged so as to bedisplaceably guided on the end area of the tubular housing remote of therotary drive and is connected to the spindle nut and articulated at thestationary structural component part or flap by its end remote of therotary drive, the part of the system that is movable in a telescopingmanner relative to the tubular housing is also externally protected.

In one embodiment, the second drive device is a gas spring and the firstwork chamber and second work chamber are filled with a gas underpressure. The gas acting upon the larger effective surface of the pistongenerates the push-out movement of the piston rod.

In one embodiment of the invention, a piston rod extension extendsfarther in the direction of the first end of the cylinder, opposite theend of the piston rod located in the cylinder. Preferably, the piston isarranged coaxial to the cylinder.

A second piston is preferably arranged at the end of the piston rodextension. The second piston is a mirror image of the first piston.

The two pistons have a closing spring with identical or different springforces.

In one embodiment, the cylinder of the second drive device has aflexible wall, particularly a dividing piston that is axiallydisplaceable in the cylinder so as to be sealed. This defines a partialspace between the closed end of the cylinder and the second work chamberin the cylinder. The partial space is filled with a gas under pressure,and the first work chamber and second work chamber are filled with anincompressible fluid, preferably an oil.

The flexible wall, holds the fluid under pressure in the second workchamber in conjunction with the gas that is under pressure to generatethe push-out movement of the piston rod by the greater effective surfaceof the piston.

In one embodiment, the valve arrangement has a closing valve with avalve element by which three switching positions can be occupied,wherein, proceeding from a middle closed switching position, a firstopening position can be occupied by the valve element in one directionand a second open position can be occupied by the valve element in theother direction.

For a further development of this closing valve, reference is made toU.S. Pat. No. 5,988,608 whose disclosure is incorporated by reference.

In another embodiment, the valve arrangement has an electricallycontrollable magnetic valve, wherein the magnetic valve is powered on toopen the flow connection between the first work chamber and the secondwork chamber by controlling the first drive device for the flapadjustment.

The valve arrangement can be arranged at any suitable location of thesecond drive device.

When the valve arrangement is arranged in or at the piston, installationspace is minimized.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of the disclosure. For a better understanding of the invention, itsoperating advantages, and specific objects attained by its use,reference should be had to the drawing and descriptive matter in whichthere are illustrated and described preferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiment examples of the invention are shown in the drawings and aredescribed more fully in the following.

FIG. 1 shows a schematic view of a motor vehicle with a swivelablydriven hatchback;

FIG. 2 shows an embodiment form of an electromechanical drive accordingto the invention;

FIG. 3 shows an embodiment form of a hydropneumatic drive according tothe invention;

FIG. 4 shows embodiment form of a hydropneumatic drive;

FIG. 5 shows embodiment form of a hydropneumatic drive;

FIG. 6 shows embodiment form of a hydropneumatic drive; and

FIG. 7 shows embodiment form of a hydropneumatic drive.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1 is a schematic view of a motor vehicle with a car body as a basicpart 1 and a movable part 3 which closes or opens an aperture 2 in thebasic part 1 and which is constructed as a hatchback, hereinafter flap3. The flap 3 can also be a front hood, an engine hood, a vehicle door,or the like.

The flap 3 is preferably mounted in a horizontal swiveling axis 4extending transverse to the vehicle. It should be noted that theswiveling axis need not be horizontal but many, for example, be verticalor any other angle. A first drive device 5 is arranged at one side ofthe flap 3 and a second drive device 6 is arranged at the opposite sideof the flap 3.

FIG. 2 depicts one of the two drive devices, embodied as anelectromechanical drive device, which is associated with the first drivedevice 5 in the following description for the sake of simplicity. Itshould be noted that the drive device shown in FIG. 2 may alternativelybe associated with second drive device 6.

The first drive device 5 has a tubular housing 7 that is closed at oneend by a base piece 8. The base piece 8 has a threaded pin 9 on which aconnection element 10 is screwed.

The housing 7 has a first portion 11, a second portion 12, and a thirdportion 13. The first portion 11 has a larger inner diameter than secondportion 12 while its outer diameter preferably remains the same. Thirdportion 13 has a larger outer diameter than second portion 12 while theinner diameter remains the same.

A protective tube 14 whose outer diameter substantially corresponds tothe outer diameter of the second portion 12 of the housing 7 is arrangedover third portion 13 of the housing 7. The protective tube 14 is closedby a base piece 15 at a remote and of the housing 7. The base piece 15has a threaded pin 16 on which a second connection element 17 isscrewed.

The connection elements 10 and 17 include a ball socket, as is shown inFIG. 2, but knuckle eyes or the like can also be used. In oneembodiment, the connection element is integral with the base piece orconnected by other connection techniques such as welding, or creasing,or the like so that the first drive device 5 is connected in anarticulated manner to a stationary structural component part of the bodyor to the basic part 1 of a motor vehicle and to a movable structuralcomponent part of the motor vehicle that is constructed as a flap 3.

A rotary drive 18 is arranged inside the housing 7 in the first portion11. The rotary drive 18 comprises an electric motor 19, a sensor devicein a sensor housing 20, and a gear unit 22 in a gear unit housing 21.The electric motor 19 is supported by the sensor housing 20 at the endof the housing 7 that is closed by the base piece 8. The gear unithousing 21 is supported at the electric motor 19 by an adapter element23. The gear unit 22 arranged in the gear unit housing 21 is driven by amotor driveshaft 24. Further, the motor driveshaft 24 projects into thesensor housing 20 on the side opposite the gear unit housing 22. Theelectrical connection lines, not shown, comprising the power supplylines and control lines extend from the sensor housing 20, through thebase piece 8 and out of the housing 7.

The gear unit housing 21 is closed at the side opposite the electricmotor 19 by a housing cover 25 through which a gear unit shaft 26extends. The end of the gear unit shaft 26 is connected to a spindledrive. An adapter insert 27 to which a spindle adapter 28 is arranged islocated at the end of the gear unit shaft 26. A threaded spindle 29 isconnected to the gear unit shaft 26 by the adapter insert 27 and spindleadapter 28.

The spindle adapter 28 is supported in a bearing 30. The bearing 30 isin turn arranged in a bearing sleeve 31 which is supported at the gearunit housing 22 or housing cover 25 on one side and contacts a step 32on the other side, which step 32 is formed by the different innerdiameters of portions 11 and 12. Accordingly, the rotary drive 18 isfixed together with the bearing 30 of the threaded spindle 29 in axialdirection inside the first portion 11 of the housing 7. Part of therotary drive 18 can be connected to the housing 7 by screws 33 orcatches in such a way that they cannot rotate relative to the housing.

A spring sleeve 34 is supported at the bearing 30 or at the bearingsleeve 31 located substantially in the second portion 12 so as tocontact the inner wall of the housing 7. A wall 35 with a bore hole 36is formed in the interior of the spring sleeve 34. The threaded spindle29 extends through bore hole 36. The spring sleeve 34 is lengthened by aguide tube 37 to the end of the housing 7 proceeding from the secondportion 12 of the housing 7 in direction of the third portion 13. Springsleeve 34 and guide tube 37 each have, at their sides contacting oneanother, projections 38 and complementary recesses 39 and areaccordingly arranged so as to be fixed with respect to rotation relativeto one another. Further, the guide tube 37 has at least one groove 40which extends in axial direction and which can also be constructed as aslot, and a projection 42 formed at a spindle nut 41 projects into thisgroove 40.

A spring device 43 which partially surrounds the threaded spindle 29extends from the side of the wall 35 remote of the bearing 30 indirection of the third portion 13 of the housing 7 and makes contactwith the spindle nut 41 running on the threaded spindle 29, inparticular when the first drive device 5 is inserted, i.e., when theflap 3 is in its almost fully closed position. The spring device 43urges the spindle nut 41 away from the wall 35 when opening the flap 3out of its completely closed position and the rotary drive 18 thereforesupports at least the first centimeter of the flap-opening movement.

An axially movable spindle tube 44 is guided with the spindle nut 41 inthe guide tube 37 and is arranged with one end at the spindle nut 41 andwith its other end at the base piece 15 of the protective tube 14. Thethreaded spindle 29 has, at the end near the base piece 15, a guide ring45 that is arranged in the spindle tube 44 to prevent radial swivelingof the threaded spindle 29.

Another guide ring 46 is arranged between the spindle tube 44 and theend of the housing 7 near the connection element 17, which also preventsa radial swiveling of the structural component parts that move in atelescoping manner and forms a stable protection against buckling.

FIG. 3 shows an example of a drive device in the form of apiston-cylinder unit 47, which is preferably associated with the seconddrive device 6.

The piston-cylinder unit 47 is preferably constructed as a gas springand is filled with a gaseous medium under pressure. The piston-cylinderunit 47 comprises a cylinder 48 with a closed first end 49 and a secondend 50 located opposite the closed end. A piston rod 51 arranged coaxialto the cylinder 48 is guided out of the cylinder 48 through the secondend 50 by a sealing and guiding package 52. Connection devices 53 and 54are arranged at the closed end 49 of the cylinder and at the end of thepiston rod 51 lying outside of the cylinder. The connection devices 53,54 can receive connection elements, not shown, such as ball sockets,knuckle eyes, or the like.

A piston 55 divides the piston-cylinder unit 47 into a first workchamber 56 on the piston rod side and a second work chamber 57 remote ofthe piston rod arranged at the end of the piston rod 51 located in thecylinder 48. The piston 55 comprises a stationary guide sleeve 58, whichhas a circumferential supporting edge 59 for a closing spring 60. Theclosing spring 60 biases a slide 61, centered with a slide sleeve 62, onthe guide sleeve 58. The closing spring 60 acts on a circular slidesurface 63 whose axial end portion cooperates with a sealing ring 64.The sealing ring 64 forms an axially movable valve element that occupiesvarious switching positions on a valve ring 65.

The outer surface of the valve ring 65 is contoured, which in oneembodiment, makes possible three switching positions. Considered fromthe slide surface 63, the valve ring 65 has a first valve seat surfacein the form of an inclined surface 66, a second valve seat surface inthe form of a clamping surface 67, and a third valve surface in the formof an inclined surface 68. It should be noted that additional surfacesare provided in other embodies to provide additional switchingpositions. A stop ring 69 clamps the entire construction of the piston55. A valve ring seal 70 prevents leakage between the pin of piston rod51 and the valve ring 65.

To allow the medium to flow faster into the area of the cylinder 48 inwhich the piston 55 is located when the flap 3 is almost closed so as toensure a more powerful lifting out of the closed position of the flap 3and falling into the flap lock, a groove 71 extending in axial directionis preferably formed in the cylinder.

FIG. 4 shows another second drive device. In many respects, thisembodiment corresponds to the embodiment shown in FIG. 2. Therefore,identical structural component parts are provided with the samereference numbers and are not described in more detail.

In contrast to the piston-cylinder unit 47 shown in FIG. 2, a dividingpiston 72 divides the second work chamber 57 remote of the piston rodinto a first partial space 73 in the vicinity of the first end 49 of thecylinder 48 and a second partial space 74 remote of the first end 49.The first partial space 73 is filled with a gas under pressure, whilethe first work chamber 56 and the second partial space 74 are filledwith oil. A sealing ring 75 is inserted into a groove 76 of the dividingpiston 72 so that the oil and gas do not mix.

To allow the oil to flow faster into the area of the cylinder 48 inwhich the piston 55 is located when the flap 3 is almost closed, agroove 71 extending in an axial direction is formed in the cylinder 48.Groove 71 is located substantially in the second partial space 73 nearthe dividing piston 72. However, a sufficient distance is provided sothat the dividing piston 72 cannot be displaced over groove 71.

FIG. 5 shows another second drive device 6. In many respects, thisembodiment corresponds to the embodiment shown in FIG. 3. Therefore,identical structural component parts are provided with the samereference numbers and are not described in more detail.

A piston rod extension 51 a extends coaxial to the cylinder 48 from theend of the piston rod 51 lying in the cylinder 48 and the piston 55arranged at the latter farther in direction of the first end 49 of thecylinder 48. A piston 55 a has the same construction and the same shapeas piston 55 but opposite orientation, and is arranged at the end of thepiston rod extension and divides the second work chamber 57 again. Thethird work chamber located opposite from the piston rod extension 51 ais designated by reference number 57 a.

In contrast to the piston-cylinder unit 47 shown in FIG. 2, a first area71 a in which there is no groove is formed near the first end 49 and asecond area 71 b in which there is no groove is formed near the sealingand guiding package 52. The groove 71 extends between first area 71 aand second area 71 b in an axial direction. The axial dimension of theareas 71 a, 71 b without grooves and of groove 71 or of the piston rodextension 51 a is determined by the application. For example, in oneembodiment the piston rod extension 51 a is longer in axial directionthan the stroke path of the piston rod 51 so that piston 55 and piston55 a never reach the same point inside the cylinder 48. Further, thefirst area 71 a in which there is no groove is long enough so that thepiston 55 a cannot move to the first end 49 of the cylinder 48 when theflap 3 is completely closed. Of course, other variations will beapparent to the person skilled in the art.

FIG. 6 shows another second drive device 6. Piston-cylinder unit 47 issimilar to the piston cylinder of 47 shown in FIGS. 3 and 4. A springreceiving part 77 is arranged at the end of the piston rod 51 projectingout of the cylinder 48 and another spring receiving part 78 is arrangedat the first end 49 of the cylinder 48. A helical pressure spring 79 isfixed coaxially around the cylinder 48 by the two spring receiving parts77 and 78.

The following describes operation of the first and second drive devices5 and 6. When the flap 3 is opened from its completely closed position,the threaded spindle 29 of the first drive device 5 is set in rotationalmovement by the rotary drive 18 so that the spindle nut 41 is moved overthe threaded spindle with the assistance of the spring device 43 so thatthe housing 7 and the protective tube 14 are displaced so that they cantelescope relative to one another.

At substantially the same time, the piston 55 of the piston-cylinderunit 47 shown in FIG. 3 is displaced in direction of the second end 50because of the pressure conditions in the cylinder 48 so that the pistonrod 51 is moved out of the cylinder 48. A relatively large amount ofmedium can flow from the first work chamber 56 into the second workchamber 57 through the groove 71. In addition, the sealing ring 64 isdisplaced in the area of the inclined surface 68 so that additional flowopenings are released.

The flap 3 can stop at any desired point in its swiveling path and theelectric motor is switched off. The electric motor 19 and the gear unit22 are not self-locking so friction is low. Movement of the flap 3 ispossible by manually applying force to the flap 3. The flap attempts tomove down into the closed position because of its own weight. However,the sealing ring 64 is moved on the clamping surface 67 because of thepressure conditions prevailing in the cylinder 48 so that the gas,preferably nitrogen, can no longer flow from the first work chamber 56into the second work chamber 57 in the cylinder 48. The flap 3 does notmove from of its completely closed position.

When the flap 3 is moved farther towards of its completely openposition, whether by applying manual force or by means of the firstdrive device 5, the sealing ring 64 is moved into the area of theinclined surface 68 and the gas can flow again from the first workchamber 56 into the second work chamber 57.

However, if the flap 3 is moved towards its completely closed position,either by manual force or by the first drive device, the piston rod 51is pushed into the cylinder 48 and the sealing ring 64 is supported atthe end portion of the slide surface 63. The sealing ring 64 is pressedagainst the slide 61 by the pressure in the second work chamber 57 andby the frictional force between the cylinder 48 and the sealing ring 64.When the sum of the frictional force and pressure force is greater thanthe closing force of the closing spring 60, the slide 61 together withthe sealing ring 64 moves in direction of the connection device 54. Thegas can flow out of the second work chamber 57 into the first workchamber 56 through a gap formed by the inclined surface 66 and thesealing ring 64.

When the piston rod 51 is not pushed in any farther, the sealing ring 64is pressed back on the clamping surface 67 again by the pressureconditions prevailing in the second cylinder 48 and by the closingspring 60.

The piston-cylinder unit 48 of the drive device 6 shown in FIG. 4 alsofunctions in a similar manner. As was already described above, only thefirst partial space 73 of the second work chamber 57 is filled with agas under pressure, whereas the first work chamber 56 and the secondpartial space 74 of the second work chamber 57 are filled with oil.Owing to the fact that the first partial space 73 is under pressure andthe dividing piston 72 is forced against the oil column, the piston rod51 attempts to move in the extended direction because of the pressureconditions and surface ratios. The switching of the sealing ring 64follows the same principles as the piston-cylinder unit described abovewith reference to FIG. 3.

In the embodiment, form of the drive device 6 shown in FIG. 5, in theclosed state of the flap 3 the piston 55 is in the area of the groove 71and the piston 55 a is in the first area 71 a in which there is nogroove. When the flap 3 is opened, the piston 55 a acts in the same wayas was described in the closing direction with reference to FIG. 3. Thepiston 55 is ineffective as long as it is moved in the extendeddirection. The push-out force acting on the piston rod 51 in the firstarea 71 a without the groove includes the gas force acting on theeffective surface of the piston 55 a and the generated holding force ofthe closing spring 60 a of the piston 55 a. When the sealing ring 64 aof the piston 55 a reaches the groove 71, the medium located in theinterior of the cylinder 47 flows around the sealing ring 64 a and thepiston 55 a acts like a conventional piston and supports the piston rod55 moving out of the cylinder 47.

In the almost completely open position of the flap 3, the piston 55 ismoved into the second area 71 b in which there is no groove andfunctions in the opening direction in the same way as describedreferring to FIG. 3. If the flap 3 is stopped, the sealing ring 64 ismoved on the clamping surface 67 because of the pressure conditionsprevailing in the cylinder 48, so that the gas in the cylinder 48 can nolonger flow from the first work chamber 56 into the second work chamber57. The weight of the flap 3 by itself is not sufficient to move towardof its completely closed position. When the flap is completely open, thepiston 55 a is located in the area of the groove 71 and the piston 55 islocated in the second area 71 b in which there is no groove.

When closing the flap 3 by manual force or by means of the first drivedevice 5, the piston 55 acts in the closing direction in the same way asdescribed referring to FIG. 3. The piston 55 a acts like a conventionalpiston by which, because of the pressure conditions prevailing in thecylinder and the effective surface of the piston 55 a, the piston rod ismoved into the cylinder 47 against the moving-out force generated inthis way. When the piston 55 a arrives in the first grooveless area 71a, it acts in the opening direction of the flap 3 as was described withreference to FIG. 2 or in the moving-out direction of the piston rod 51.If the flap 3 is stopped, the sealing ring 64 a moves on the clampingsurface 67 a because of the pressure conditions prevailing in thecylinder 48 so that the gas in the cylinder 48 can no longer flow fromthe third work chamber 57 a into the second work chamber 57.

The closing springs 60 and 60 a installed in the pistons 55 and 55 a canhave different or identical spring forces in order to achieve differentswitching behavior of the piston in the push-out or push-in directions.

Further, the helical pressure spring 79, which is shown in FIG. 6arranged coaxially around the piston-cylinder unit 47, increases theextension force of the piston-cylinder unit 47 and compensating fortemperature-dependent pressure changes inside the cylinder 48.

FIG. 7 shows another embodiment of the second drive device 6, parts ofwhich correspond to the embodiment shown in FIG. 3.

The piston-cylinder unit comprises a closed cylinder 248, which ispreferably filled with an incompressible fluid under pressure. Theinterior of the cylinder 248 is divided into a first work chamber 256and a second work chamber 257 by a piston 255, which is axiallydisplaceable in the cylinder 248. A piston rod 251 is arranged at oneside of the piston 255 and is guided through the first work chamber 256and outward at the seal end 250 of the cylinder 248. A passage 80leading from the first work chamber 256 to the second work chamber 257can be opened and closed by an electrically controllable magnetic valve81.

The end of the piston rod 251 projecting into the cylinder 248 isprovided with a coaxial threaded bore hole, 82 a (shown in dottedlines), in which a bolt-shaped coil core 82 having a smaller diameterthan the piston rod 251 is screwed in by its end which is provided witha thread so that the coil core 82 forms a coaxial extension of thepiston rod 251. Other connection possibilities such as, e.g., welding,are also conceivable.

An electrically insulating spacer disk 83 of is arranged on the end ofthe piston rod 251 projecting into the cylinder 248 and engages aroundthe end of the piston rod on the radial inner side. An insulating ring84 is arranged on the coil core 82 so as to contact the spacer disk 83axially and is contacted axially in turn by an annular disk 85 of steelwhich extends radially outward into the vicinity of the inner wall ofthe cylinder 248.

An electrically insulating coil carrier 86 preferably encloses the coilcore 82 and is arranged on the coil core 82 on the side of the disk 85remote of the insulating ring 84 and contacts the disk 85 axially by aradial flange 87. A coil 90 to which current can be applied is locatedbetween two radial flanges 88 and 89 of the coil core 86 which arearranged at a distance from one another.

A circular disk 91 of paramagnetic material is preferably fixedlyarranged on the end of the coil core 82 which is remote of the pistonrod 251 and which projects out of the coil carrier 86, this circulardisk 91 contacting the coil carrier 86 axially by one of its ends andholding the latter in contact with the disk 85 by its flange 87.

The circular disk 91 extending radially to the vicinity of the innerwall of the cylinder 248 is formed with continuous axial openings 92which are arranged so as to be uniformly distributed on a concentriccircle, and the free ends of correspondingly axially extending pins 93of a circular-cylindrical piston part 94 of paramagnetic materialproject into the axial openings 92 and are fastened. The piston part 94is guided in the cylinder 248 so as to be axially displaceable and hasan annular groove 95 at its radially circumferential outer surface.

Two guide rings 96 of electrically nonconductive material are insertedinto the annular groove 95 at the two axial ends in such a way that theyextend radially until contacting the inner wall of the cylinder 248 foraxially guiding the piston part 94.

A sealing ring 97 is inserted into the annular space of the annulargroove 95 formed axially between the two guide rings 96 and contacts theinner wall of the cylinder 248 with its outer radially circumferentialannular surface and seals the two work chambers 256 and 257 relative toone another.

The coaxially continuous passage 80 is formed in the piston part 94 andits opening facing the coil core 82 forms a valve seat 98.

A disk-like armature 99 with axial play is arranged so as to be movableaxially between the front side of the piston part 94, from which thepins 93 protrude axially, and the free end of the coil core 82. Thedisk-like armature 99 carries on its side facing the valve seat 98 avalve closing member 100 which is formed as an elastomer part and bywhich the passage 80 is closed when contacting the piston part 94axially.

The disk-shaped armature 99, which extends radially to the vicinity ofthe inner wall of the cylinder 248, has axial recesses 101 correspondingto the pins 93 which project through these axial recesses 101.

Accordingly, the armature 99 is guided on the pins 93 so as to beaxially displaceable. The armature 99 is acted upon with its valveclosing member 100 axially against the valve seat 98 by a pretensionedpressure spring, which is supported at the circular disk 91 andconstructed as a spring ring 102.

In this embodiment, power is supplied externally by the piston rod 251to the first coil end 103 of coil 90. The second coil end 104 of thecoil 90 leads to an annular sliding contact 105 which is clamped axiallybetween the spacer disk 83 and the insulating ring 84 and whose slidingarms 106, which project outward approximately radially, contact theinner wall of the grounding cylinder 248 so as to be pretensioned in aspringing manner.

In order to move the flap 3, the first drive devices is controlled insuch a way that the rotary drive 18 sets the threaded spindle 29 inrotation, and the housing 7 and the protective tube 14 are movedrelative to one another. At the same timer, the coil 90 of the seconddrive device 6 is energized so that the passage 80 in the piston 255 isreleased and the piston 255 can move in axial direction. When the flapis stopped in a determined position, the two drive devices 5 and 6 areturned off. The passage 80 in the second drive device 6 is closed sothat the piston 255 and the piston rod 251 can no longer be moved. Thesecond drive device 6 then holds the flap securely in the adjustedposition.

Thus, while there have shown and described and pointed out fundamentalnovel features of the invention as applied to a preferred embodimentthereof, it will be understood that various omissions and substitutionsand changes in the form and details of the devices illustrated, and intheir operation, may be made by those skilled in the art withoutdeparting from the spirit of the invention. For example, it is expresslyintended that all combinations of those elements and/or method stepsthat perform substantially the same function in substantially the sameway to achieve the same results are within the scope of the invention.Moreover, it should be recognized that structures and/or elements and/ormethod steps shown and/or described in connection with any disclosedform or embodiment of the invention may be incorporated in any otherdisclosed or described or suggested form or embodiment as a generalmatter of design choice. It is the intention, therefore, to be limitedonly as indicated by the scope of the claims appended hereto.

1. A system for opening and closing a flap for a motor vehicle, the flapbeing mounted along one of its edges at a stationary structuralcomponent of the motor vehicle so as to be swivelable around a swivelingaxis so as to be movable between a closed position and an open position,the system comprising: a first non-self-locking drive device coupledbetween the flap and the stationary structural component, the firstdrive device being an electromechanical drive device; and a second drivedevice acting in parallel with the first drive device, the second drivedevice being one of a hydraulic, pneumatic, and hydropneumatic drivedevice, the second drive device comprising: a cylinder having a firstclosed end articulated at one of the stationary structural componentpart and the flap at a distance from the swiveling axis, the cylinderbeing at least partially filled with a fluid under pressure; a pistonthat divides an interior of the cylinder into a first work chamber and asecond work chamber; a piston rod coupled to the piston, the piston rodbeing guided outward through and out of the first work chamberarticulated at the other of the flap or the stationary structuralcomponent part at a distance from the swiveling axis; a sealing andguiding package adapted to guide the piston rod through and out of thefirst work chamber; and a valve arrangement forming a flow connectionbetween the first work chamber and the second work chamber, wherein thevalve arrangement is closed when the flap is stationary.
 2. The systemfor opening and closing a flap according to claim 1, wherein the firstdrive device is arranged at a first edge area of the flap and the seconddrive device is arranged at a second edge area of the flap, each edgeextending at substantially a right angle from the swiveling axis.
 3. Thesystem for opening and closing a flap according to claim 1, wherein theflap is one of a hatchback, a trunk hood, and an engine hood.
 4. Thesystem for opening and closing a flap according claim 1, wherein theflap is supported along an edge area so as to be substantially verticalin the closed position and substantially horizontally in the openposition.
 5. The system for opening and closing a flap according claim1, wherein the first drive device comprises: a rotary drive; a threadedspindle coupled to the rotary drive and adapted to rotatably drive thethreaded spindle, the threaded spindle coupled to one of the flap andthe stationary structural component part; and a spindle nut arranged onthe threaded spindle coupled to the other of the stationary structuralcomponent part and the flap.
 6. The system for opening and closing aflap according to claim 5, further comprising a non-self-locking gearunit coupled between the threaded spindle and the rotary drive.
 7. Thesystem for opening and closing a flap according to claim 5, wherein therotary drive is an electric motor.
 8. The system for opening and closinga flap according to claim 5, further comprising a tubular housing inwhich at least the rotary drive, the threaded spindle, and the spindlenut are arranged.
 9. The system for opening and closing a flap accordingto claim 5, further comprising a spindle tube adapted to enclose thethreaded spindle, the spindle tube being connected to the spindle nut atits axial end closer to the rotary drive and is coupled to one of thestationary structural component part and the flap at its axial endremote of the rotary drive.
 10. The system for opening and closing aflap according to claim 8, further comprising a protective tubeconnected to the spindle nut on the end area of the tubular housingremote of the rotary drive coupled to the stationary structuralcomponent part or flap by its end remote of the rotary drive.
 11. Thesystem for opening and closing a flap according to claim 1, wherein thesecond drive device is a gas spring, the first work chamber and secondwork chamber being filled with a gas under pressure.
 12. The system foropening and closing a flap according to claim 11, further comprising apiston rod extension extending from the end of the piston rod, whereinthe piston, the piston rod, and the piston rod extension are arrangedcoaxial to the cylinder.
 13. The system for opening and closing a flapaccording to claim 12, further comprising a second piston arranged atthe end of the piston rod extension.
 14. The system for opening andclosing a flap according to claim 13, wherein the piston has a closingspring and the second piston has a second closing spring, wherein theclosing springs having substantially identical or different springforces.
 15. The system for opening and closing a flap according toclaims 1, wherein the cylinder of the second drive device has a dividingpiston, the dividing piston being axially displaceable in the cylinderdefining a partial space between the closed end of the cylinder and thesecond work chamber in the cylinder, wherein the partial space is filledwith a gas under pressure.
 16. The system for opening and closing a flapaccording to claims 15, wherein the first work chamber and second workchamber are filled with an incompressible fluid.
 17. The system foropening and closing a flap according to claims 16, wherein theincompressible fluid is an oil.
 18. The system for opening and closing aflap according to claim 1, wherein the valve arrangement includes aclosing valve having a valve element by which three switching positionscan be occupied, wherein, proceeding from a middle closed switchingposition, a first opening position can be occupied by the valve elementin one direction and a second open position can be occupied by the valveelement in the other direction.
 19. The system for opening and closing aflap according to claim 1, wherein the valve arrangement is anelectrically controllable magnetic valve.
 20. The system for opening andclosing a flap according to claim 19, wherein the magnetic valve ispowered on so as to open the flow connection between the first workchamber and the second work chamber by controlling the first drivedevice for the flap adjustment.
 21. The system for opening and closing aflap according to claim 20, wherein the valve arrangement is arranged inthe piston.